Verlag Dr. Friedrich Pfeil ISSN 0936-9902 Ichthyological Exploration of Freshwaters An international journal for fi eld-orientated ichthyology Volume 21 Number 1 Ichthyological Exploration of Freshwaters An international journal for fi eld-orientated ichthyology Volume 21 • Number 1 • March 2010 pages 1-96, 62 fi gs., 14 tabs. Managing Editor Maurice Kottelat, Route de la Baroche 12, Case postale 57 CH–2952 Cornol, Switzerland Tel. + 41 - 32 - 4 62 31 75 / Fax + 41 - 32 - 4 62 22 59 / E-mail [email protected] Editorial board Pier Giorgio Bianco, Dipartimento di Zoologia, Università, Napoli, Italy Ralf Britz, Department of Zoology, The Natural History Museum, London, United Kingdom Sven O. Kullander, Naturhistoriska Riksmuseet, Stockholm, Sweden Helen K. Larson, Museum and Art Gallery of the Northern Territory, Darwin, Australia Lukas Rüber, Department of Zoology, The Natural History Museum, London, United Kingdom Ivan Sazima, Museu de Zoologia, Unicamp, Campinas, Brazil Paul H. 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Freshwaters, Vol. 21, No. 1, pp. 63-72, 3 figs., 1 tab., March 2010 © 2010 by Verlag Dr. Friedrich Pfeil, München, Germany – ISSN 0936-9902 An overview of North America’s diminutive freshwater fish fauna Micah G. Bennett* and Kevin W. Conway* Based on a review of the literature, we compile a table of North American freshwater fishes with maximum standard length (SL) less than or equal to 50 mm and information on size at sexual maturity. Using previously published criteria for miniature fishes (< 26 mm maximum SL, or those that mature at SL < 20 mm), we found evidence for seven miniature fishes on the North American continent: Elassoma alabamae, E. zonatum, Leptolucania ommata, Heterandria formosa, Megupsilon aporus, Cyprinodon macularius and Notropis saladonis, the smallest being E. alabamae (Spring Pygmy Sunfish, maximum size 25.5 mm SL). We compare the number of miniature species in North America to those from Africa, South Asia and South America and discuss patterns of distribution, habitat preference and imperilment amongst North America’s smallest freshwater fishes. Introduction brate species (P. progenetica), maturing at sizes under 8 mm in standard length (SL). The North American continent contains one of Though small-bodied fishes have always been the most diverse temperate freshwater fish faunas of interest, ichthyologists have only fairly re- in the World (Abell et al., 2000; Lundberg et al., cently began to undertake continent-wide assess- 2000), with over 1050 described and numerous ments of small-bodied species. Weitzman & Vari undescribed species (Page & Burr, 1991; Lundberg (1988) undertook the first such survey document- et al., 2000). At the turn of the 20th century the ing the numerous miniature freshwater fish spe- North American ichthyofauna was credited with cies of South America. They defined miniature the distinction of having some of the “smallest fishes as those no greater than 26 mm SL or ma- known fishes and at the same time the smallest turing at sizes smaller than 20 mm SL and identi- known vertebrates” (Smith, 1902). In more recent fied 85 such species. Costa & Le Bail (1999) years the North American continent has lost its added 26 more to the count for South America. “smallest vertebrate” status, which has passed Using Weitzman & Vari’s criterion, Kottelat & back and forth between Indo-Pacific, Australa- Vidthayanon (1993) provided a list of miniature sian and South East Asian countries (Herre, 1929; fishes for south and southeast Asia and, more Winterbottom & Emery, 1981; Watson & Walker, recently, Conway & Moritz (2006) compiled a 2004). Among these is the recent description of similar list for Africa. Besides providing a more the cypriniform genus Paedocypris (Kottelat et al., thorough knowledge of continental biodiversity, 2006), which contains the smallest living verte- identifying and tabulating the number of small- * Department of Biology, Saint Louis University, 3507 Laclede Avenue, St. Louis, MO 63103, USA. E-mail: [email protected], [email protected] Ichthyol. Explor. Freshwaters, Vol. 21, No. 1 64 bodied fishes is important to largescale ecological Results and evolutionary investigations such as those focused on geographic gradients in body size Our survey documented 146 species of North (e.g., Belk & Houston, 2002; Knouft, 2004), phy- American freshwater fishes with a maximum SL logenetic trends in body size (e. g., Knouft & Page, less than, or equal to, 50 mm, 6 of which mature 2003; Ruber et al., 2007), life history evolution at sizes of less than 20 mm SL (Table 1). The pool (e. g., Weitzman & Vari, 1988), and issues of con- of diminutive fishes (equal to or below 50 mm servation concern, such as size-biased extinction SL) covers a broad range of North American fish risks (e. g., Olden et al., 2007). families but is made up largely of Poeciliidae In this paper we provide a list of all North (32.0 %), Cyprinidae (18.4 %), Cyprinodontidae American freshwater fishes with a maximum SL (17.0 %), and Percidae (14.3 %). Three of these, less than or equal to 50 mm in order to assess the Cyprinidae, Percidae and Poeciliidae are the whether the North American ichthyofauna con- most diverse families of fishes in North America, tains any miniature species of fish (sensu Weitz- making up about 26 %, 16 % and 8 %, respec- man & Vari, 1988) and to determine the smallest tively, of that fauna (Page & Burr, 1991; Lundberg North American fish species. et al., 2000; Jelks et al., 2008), whereas the Cyprin- odontidae accounts for a much smaller portion of that fauna (less than 4 %; Jelks et al., 2008). Methods Thus the composition of Table 1 is not merely reflective of the overall pattern of North American We conducted surveys of peer-reviewed literature freshwater fish diversity. Using the definition of and books on fishes and fish biology using four Weitzman & Vari (1988) seven of these 146 species standard publication databases (Web of Science, are considered miniature: Elassoma alabamae Biological Abstracts, Google Scholar, JSTOR) and (Fig. 1), Leptolucania ommata (Fig. 2), Heterandria compiled a table of all freshwater fishes with a formosa, Megupsilon aporus (Fig. 3), Cyprinodon maximum standard length (SL) of less than or macularius, Notropis saladonis and Elassoma zon- equal to 50 mm that inhabit North America (in- tatum. Elassoma alabamae is the only species con- cluding Mexico). This was necessarily an arbitrary sidered a miniature based on maximum known cut-off point, but it was chosen in order to include size (25.5 mm SL). The remaining miniatures are the lower tail of the size distribution of North defined as such based on minimum size at ma- American freshwater fishes (sensu Knouft & Page, turity as all achieve maximum standard lengths 2003) and to include any miniature species greater than 26 mm. (< 26 mm maximum SL, sensu Weitzman & Vari, 1988). We used the University of Michigan Mu- seum of Zoology online catalogue of the Division Discussion of Fishes (UMMZ, 2009) which includes SL infor- mation to determine if specimens larger than those In comparison to other continents for which lists documented in the literature survey had been of miniature freshwater fishes have been compiled collected for species for which maximum standard (South America – Weitzman & Vari, 1988; South- lengths had been published. That catalogue also east Asia – Kottelat & Vidthayanon, 1993; Africa served as a source of information for species for – Conway & Moritz, 2006) North America has which no literature could be found. Literature few truly miniature freshwater fish species. Af- information was also used to compile data on the rica contains 24 miniature freshwater fish species minimum SL at maturity of all species with (Conway & Moritz, 2006), South